Severe drought-influenced composition and δ13C of plant and soil n-alkanes in model temperate grassland and heathland ecosystems

Abstract

Drought events are predicted to increase under future climate change. In temperate ecosystems, plants are capable of resisting drought due to their hydrophobic wax layer, in which n-alkanes are important constituents. In soils, plant-derived n-alkanes are comparatively resistant to degradation. To improve understanding of the significance of n-alkanes in plant-soil systems during a severe drought period (104 days), we investigated bulk organic carbon (Corg) concentration, total lipid extract (TLE) concentration, n-alkane molecular ratios such as average chain length (ACL), carbon preference index (CPI) and chain length ratios of different n-alkane compounds, in addition to the compound-specific isotope composition (13C) of n-alkanes in model temperate grassland and heathland plant-soil systems. Although plant communities of two (heathland) and four (grassland) species were available, only one representative species per biome was accessible for the current study. Heathland plants and soil revealed significantly higher concentrations of Corg and TLE compared with grassland. TLE and alkane composition responded quickly during the first drought phase (0-40 days). This indicates that plants were actively utilizing C and produced more n-alkanes in order to withstand drought, which was confirmed by increased (2-3‰) 13C values for n-alkanes in shoot biomass. However, during later drought phases all the parameters remained constant for plants and soils. This suggests limited change in biosynthesis and cycling of plant lipids such as n-alkanes during intense drought. Surprisingly, during the first drought phase, increased ACL and CPI ratios in soil demonstrated a rapid input of plant-derived long chain n-alkanes to soil, which was not expected due to the decadal residence time of alkanes in soil. The study enabled tracing of plant metabolic response in terms of alkane biosynthesis under different phases of drought and rapid cycling of alkanes in the plant-soil system.

Influence of earthworms on apolar lipid features in soils after 1 year of incubation

“…2% and 10% of TLE for plant residue and soil samples, respectively (Table 1). These bulk proportions are in agreement with those generally reported for plants and soils (Quénéa et al 2004;Nguyen Tu et al 2011;Srivastava & Wiesenberg 2018). The distribution of apolar lipids is shown as histograms in Fig.…”

Asynchronous variations of East Asian summer monsoon, vegetation and soil formation at Yulin (North China) in the Holocene

“…To date, they have been widely used in studies of marine sediments (Tierney and DeMenocal, 2013), lake sediments (Aichner et al , 2015; Hou et al , 2018; Rao et al , 2016; Zhao et al , 2021), peat (Huang et al , 2018; Huang and Meyers, 2019) and loess (Xie et al , 2003; Zhang et al , 2006; Wang et al , 2018, 2021). With increasing aridity, plants will have a higher productivity for leaf wax, thus the concentration of soil n ‐alkanes might be used as a proxy for climatic aridity (Hoffmann et al , 2013; Ni et al , 2015; Srivastava and Wiesenberg, 2018). As the composition of vegetation determines the distribution of different carbon numbers of these long‐chain n ‐alkane homologues, proxies such as the carbon number of the most abundant homologue (C max ) and the average chain length (ACL) can be used to infer changes in vegetation in the sedimentary record (Eglinton and Eglinton, 2008), which has been widely used in the Chinese loess plateau (CLP) records (Zhang et al , 2006; Zhou et al , 2016; Xue et al , 2016; Chen et al , 2020).…”

Understanding physiological and morphological traits contributing to drought tolerance in barley

“…Drought stress severely reduces plant growth and development by reduction in turgor pressure, cell elongation and expansion due to the osmotic stress (Farooq, Wahid, Kobayashi, Fujita, & Basra, ). Plants have developed multiple mechanisms through integrated morphological and physiological responses to survive under drought stress conditions such as deep root system (Chloupek, Dostál, Středa, Psota, & Dvořáčková, ), manipulation of stomata (Franks, W Doheny‐Adams, Britton‐Harper, & Gray, ), deposition of cuticular wax or cutinisation on leaf surface (Srivastava & Wiesenberg, ), leaf rolling (Zhang et al., ), increasing leaf thickness and succulence (Oliveira, Meyer, Afonso, & Gonçalves, ), osmotic adjustment through organic and inorganic compatible solutes (Turner, ). Among these adaptive mechanisms, stomatal and residual transpiration control and root system development are essential to the survival of plants under drought stress conditions.…”